Internet access on-board moving vehicles is in demand as mobility has become part of the daily experience. Cheap and high-quality Internet access from moving vehicles to stay connected while traveling is increasingly desirable among Internet users. Cellular networks can provide such connectivity with current practices, but they tend to be expensive. At the same time, there is an increasingly ubiquitous deployment of inexpensive 802.11-based (WiFi) networks, and in many cases, entire cities are being covered.
The ubiquity of WiFi deployments, with existing practices, can possibly support common applications, such as Web browsing, instant messaging, and voice over IP (VoIP), from moving vehicle. Current development efforts have focused on connectivity from vehicles to open-access base-stations rather than continuous connectivity across a series of base-stations. Other practices also propose application specific techniques or new applications that may work well in such environments. Current practices consider a number of operations and features including using multiple base-stations (BSes), opportunistic routing in static mesh networks, network access from moving vehicles, and fast handoffs.
Regarding the use of multiple BSes, multiple BSes can act in concert to improve client performance. Such methods exist in the domain of both cellular and WiFi communication. The cellular methods, however, require tight integration with the physical layer and strict timing across BSes. Additionally, these abilities can require expensive BS hardware which is not suitable for commodity wireless deployments. In the WiFi context, various techniques including Distributed Radio Bridges, Divert, and MRD use multiple BSes as well, to improve client performance in enterprise WLAN deployments. The BS coordination mechanism in these systems assumes that a high-capacity LAN is available. For instance, in MRD, BSes can coordinate by sending received frames to a central controller that is responsible for forwarding a copy to the Internet. Thus, if clients typically reach three BSes, the required LAN capacity is at least three times the cumulative sending rate of all clients.
Also, MultiNet, FatVAP, and PERM techniques enable clients to associate with more than one nearby BS, for instance, to increase throughput if the wireless capacity is greater than the capacity of individual wired links behind the BSes. These systems, however, do not focus on improving connectivity of the client-BS communication.
In the context of opportunistic routing (OR), OR can deploy one o more protocols such as ExOR and MORE to operatively leverage opportunistic receipt of packets with low coordination overhead. This approach considers batching wireless communication data packets to amortize overhead across the batch. Batching, however, is unsuitable for most interactive uses. For instance, voice over Internet protocol (VoIP) cannot afford the delay associated with waiting for the packets communicated by such protocols. For short transfer control protocol (TCP) transfers, the sender's congestion window will frequently be smaller than the batch size. Also, even for large data transfers, batching may interact poorly with TCP's rate control.
Furthermore, current developments to improve WiFi performance for vehicular access is generally based on controlled settings, with near line-of-sight connectivity and little interference. Recent work has shown that connectivity between individual BSes and vehicular clients is often interrupted by gray periods. Current practices consider transferring data using TCP through individual BSes as the vehicle drives by them, without maintaining connections across each of the BSes. However, performance in this setting is severely hindered by overheads at several layers, such as dynamic host control protocol (DHCP) and aggressive TCP backoffs due to losses. Current practices also consider equipping vehicles with directional antennae to improve the performance of the communications link. While directional antennae extend reach, they do not prevent connectivity disruptions that can occur even close to BSes.
From the foregoing it is appreciated that there exists a need for systems and methods to ameliorate the shortcomings of existing practices.